Recording apparatus

ABSTRACT

In second transport means ( 12 ), nipping pressure of each of outermost star wheels ( 6   a ), ( 6   e ) located at opposite ends in the primary scanning direction is set higher than that of each of star wheels ( 6   b ) to ( 6   d ) within a range lower than nipping pressure of first transport means. If a leading edge of a recording medium ( 1 ) is in a downwardly deformed state when reaching the second transport means ( 12 ), such deformation acts to press the wheels ( 6   a ) to ( 6   e ) upwardly. However, the nipping pressure of each of the opposite end star wheels ( 6   a ), ( 6   e ) nipping angular portions of the medium ( 1 ) on the leading edge side is set high enough to rectify such deformation at the angular portions. Accordingly, the medium ( 1 ) is nipped between a second driving roller ( 5 ) and the wheels ( 6   a ) to ( 6   e ) with its deformed angular portions rectified, and hence is transported in an ideal condition.

TECHNICAL FIELD

The present invention relates to recording apparatuses of the typeconfigured to jet ink against a recording medium being transported, suchas ink jet printers, and more particularly to such a recording apparatuscapable of transporting recording media properly.

BACKGROUND ART

FIG. 1 schematically illustrates the recording medium transportmechanism of a conventional ink jet printer. The conventional ink jetprinter includes a first driving roller (which, together with a firstdriven roller 4, constitutes first transport means) 3 located upstreamof a carriage unit 2 having an ink head 7 in a direction in whichrecording medium 1 is transported and is configured to transportrecording medium 1 such as a recording sheet to a location just below anink jet nozzle 7 of the carriage unit 2 where recording medium 1 is tobe temporarily halted, and then move the carriage unit 2 in a direction(primary scanning direction) perpendicular to the recording medium 1transport direction for printing on the recording medium 1. Thereafter,the ink jet printer advances the recording medium 1 by means of thefirst driving roller 3 again so that a portion of the recording medium 1to be subjected to printing next is located just below the ink head 7and then moves the carriage unit 2 during temporary stop of recordingmedium 1 for printing. These operations are repeated to form an image onwhole one side of recording medium 1.

In order to increase the printing speed of such a recording apparatuswithout varying the speed of movement of the carriage unit 2 and therecording medium transport speed, the recording medium 1 is moved by themaximum printable width of the ink head 7 for each advance thereof.Thus, the movement of the carriage unit 2 and the advance of therecording medium 1 are repeated. If moving ranges of the ink head 7 aremade to overlap each other with the amount of each advance of therecording medium 1 reduced, inks can be jetted onto the same portion ofthe recording medium 1 in an ink-on-ink manner thereby printing an imageof higher definition.

On the downstream side of the carriage unit 2 is disposed a secondtransport means for transporting and ejecting the recording medium 1,the second transport means comprising a second driving roller 5 to whicha rotational force is transmitted, and a star wheel 6 which is driven torotate while nipping the recording medium 1 between itself and thesecond driving roller 5. The star wheel 6 forming part of the secondtransport means has sharp teeth circumferentially thereof and issupported so as to be capable of coming into contact with and separatingfrom the periphery of the second driving roller 5 by means of anon-illustrated spring member. The star wheel 6 biases the recordingmedium 1 toward the second driving roller 5 by the elastic force of thespring member (see Japanese Patent Laid-Open Publication No. H08-208094for example.)

However, in the ink jet printer configured to repeat a sequence ofadvancing and temporarily halting the recording medium 1 and moving thecarriage unit 2, it is possible that the recording medium 1 stops beingtransported when the leading edge of recording medium 1 reaches alocation just past the nipping position between the second drivingroller 5 and the star wheel 6, i.e., the position where the recordingmedium 1 receives the transporting force from the second driving roller5. In this case, since the star wheel 6 is supported so as to be capableof coming into contact with and separating from the periphery of thesecond driving roller 5, it is possible that the second driving roller 5and the star wheel 6 fail to ideally catch the recording medium 1therebetween when the leading edge of the recording medium 1 is not in agood condition. For this reason, the second driving roller 5 and thestar wheel 6 cannot reliably transport the recording medium 1, thusraising a problem of unstable transport of recording medium 1.

For example, when the leading edge of recording medium 1 is deformeddownwardly as shown in FIG. 2, the leading edge is brought into contactwith the second driving roller 5 first and then raised as kept deformeddownwardly as the second driving roller 5 rotates, thereby pressing thestar wheel 6 upwardly away from the second driving roller 5. When thestar wheel 6 becomes separated from the second driving roller 5, thestar wheel 6 cannot rotate because the star wheel 6 does not directlyreceive the rotational force but is driven to rotate by the seconddriving roller 5. In such a case the star wheel 6 becomes an obstacle totransport of the recording medium 1. Thus, it becomes possible for thestar wheel 6 to facilitate deformation of recording medium 1 or damagethe recording medium 1 and, in the worst case, to cause jam to occur.

To avoid such a phenomenon, it is conceivable that the star wheel 6 isconfigured to apply the recording medium 1 with sufficient pressure torectify the deformed condition of the leading edge of recording medium 1to an ideal condition. However, if the second driving roller 5 ispressurized excessively by the star wheel 6, large load fluctuationsoccur when the recording medium 1 advances to the contact positionbetween the second driving roller 5 and the star wheel 6, so that smoothtransport of the recording medium 1 is impeded on the contrary. Also,since the periphery of the star wheel 6 comprises a multiplicity ofsharp teeth, application of excessive pressure to the recording medium 1by the star wheel 6 will result in a problem of damage to the surface ofrecording medium 1.

Such problems are common to recording apparatuses of the type havingtransport means comprising a roller pair including a star wheel as adriven roller, as well as to ink jet printers.

An object of the present invention is to provide a recording apparatuswhich is capable of reliably nipping a recording medium by secondtransport means including a star wheel without the need to applyexcessive pressure onto the recording medium from the star wheel evenwhen a leading edge portion of the recording medium has somedeformation, thereby constantly ensuring smooth and stable transport ofthe recording medium.

DISCLOSURE OF THE INVENTION

The present invention provides the following arrangements as means forsolving the aforementioned problems.

(1) A recording apparatus wherein: a recording medium is transported byfirst and second transport means nipping the recording medium; and thesecond transport means comprising plural roller pairs arranged in adirection perpendicular to a recording medium transport direction and isdisposed downstream of the first transport means in the recording mediumtransport direction, characterized in that

each of the roller pairs of the second transport means is set to have alower nipping pressure than the first transport means, while anoutermost one of the roller pairs set to have a higher nipping pressurethan the rest of the roller pairs.

In this arrangement, the second transport means comprising the pluralroller pairs arranged in the direction perpendicular to the recordingmedium transport direction is disposed downstream of the first transportmeans, and each of the roller pairs of the second transport means is setto have a lower nipping pressure than the first transport means, whilethe outermost one of the roller pairs set to have a higher nippingpressure than the rest of the roller pairs.

Deformation of the recording medium occurs frequently at angularportions of the recording medium. Though jam is most likely when suchdeformation occurs, rectification of the deformation at the angularportions allows deformation at a central portion of the recording mediumto be rectified relatively easily following the rectification of thedeformation at the angular portions. Thus, it becomes possible totransport the recording medium in an ideal condition. Also, because theangular portions of the recording medium are not constrained on one sidein the direction perpendicular to the recording medium transportdirection, the deformation at the angular portions can be rectified witha weaker external force than is required to rectify the deformation atthe central portion.

Thus, with the arrangement wherein only the opposite outermost ones ofthe plural roller pairs arranged in the direction perpendicular to therecording medium transport direction, which are adapted to contactportions of the recording medium adjacent to the angular portions, areeach set to have a nipping pressure which is increased by a necessaryand sufficient value for rectification of the deformation at the angularportions of the recording medium within a range that is lower than thenipping pressure of the first transport means, while the rest of theplural roller pairs, including a centrally positioned roller pair, isset to have a lower nipping pressure than the opposite outermost rollerpairs, there is no possibility that the recording medium is applied withan excessive nipping pressure and the sum total of the nipping pressuresof the plural roller pairs forming the second transport means increasesconsiderably. Thus, there is no possibility that the surface of therecording medium is damaged and large load fluctuations occur upon entryof the recording medium into the second transport means. Accordingly,this arrangement can assuredly rectify the deformation at the angularportions of the recording medium without any impediment to smoothtransport of the recording medium.

(2) The plural roller pairs of the second transport means are disposedto have plural nipping positions in the recording medium transportdirection such that the outermost one of the plural roller pairs isdifferent in nipping position from the rest of the plural roller pairs.

In this arrangement, the outermost one of the plural roller pairsforming the second transport means, which is set to have a highernipping pressure than the rest of the plural roller pairs, is disposedso as not to have a nipping position coinciding with that of the rest inthe recording medium transport direction. Accordingly, the relativelyhigh nipping pressure of the outermost roller pair and the nippingpressure of the rest are not exerted on the leading edge portion of therecording medium being transported at a time. Thus, there is nopossibility that large load fluctuations occur upon entry of therecording medium into the second transport means. For this reason, thisarrangement can assuredly rectify the deformation at the angularportions of the recording medium without any impediment to smoothtransport of the recording medium.

(3) The plural roller pairs of the second transport means are disposedto have plural nipping positions in the recording medium transportdirection such that a central one of the plural roller pairs has anipping position located most upstream.

In this arrangement, the central one of the plural roller pairs formingthe second transport means, which has a lower nipping pressure than theopposite end roller pairs, has a nipping position located most upstreamin the recording medium transport direction. Accordingly, the relativelylow nipping pressure is initially exerted centrally of the leading edgeportion of the recording medium having reached the second transportmeans. Thus, there is no possibility that large load fluctuations occurupon entry of the recording medium into the second transport means. Forthis reason, this arrangement can assuredly rectify deformation at theangular portions of the recording medium without any impediment tosmooth transport of the recording medium.

(4) The plural roller pairs of the second transport means are disposedto have plural nipping positions in the recording medium transportdirection such that any one of the roller pairs which is locatedimmediately downstream of an upstream one of the roller pairs in therecording medium transport direction has a higher nipping pressure thanthe upstream one.

In this arrangement, the plural roller pairs forming the secondtransport means are disposed to have plural nipping positions in therecording medium transport direction such that any one of the rollerpairs which is located immediately downstream of an upstream one of theroller pairs in the recording medium transport direction has a highernipping pressure than the upstream one. Accordingly, graduallyincreasing nipping pressure is exerted on the leading edge portion ofthe recording medium being transported and, hence, there is nopossibility that a high nipping force is abruptly exerted on the leadingedge portion. Thus, there is no possibility that large load fluctuationsoccur upon entry of the recording medium into the second transportmeans. For this reason, this arrangement can assuredly rectifydeformation at the angular portions of the recording medium without anyimpediment to smooth transport of the recording medium.

(5) The second transport means is configured to transport the recordingmedium at a higher speed than the first transport means.

In this arrangement, the recording medium transport speed of the secondtransport means is higher than that of the first transport means locatedupstream of the second transport means. Accordingly, a largertransporting force is exerted on the recording medium on the downstreamside than on the upstream side in the transport direction and, hence,there is no possibility that the recording medium becomes deflectedbetween the first and second transport means. Also, tension working inthe transport direction is exerted on the recording medium beingtransported, so that deformation of the recording medium is rectifiedmore effectively.

(6) A plurality of such second transport means are arranged in therecording medium transport direction.

In this arrangement, the plurality of second transport means arearranged downstream of the first transport means in the recording mediumtransport direction. Accordingly, the recording medium being transportedis kept nipped at two points in the transport direction during a periodjust after passage of the trailing edge thereof through the firsttransport means until arrival thereof at the second transport means.Thus, even when the recording medium is deformed at angular portions onthe trailing edge side thereof, this arrangement can rectify suchdeformation by means of the roller pairs located at opposite ends in thedirection perpendicular to the transport direction while keeping thesurface of the recording medium parallel with the transport direction,whereby smooth transport can continue until the trailing edge of therecording medium passes through the second transport means.

(7) Each of the roller pairs forming the second transport meanscomprises a driving roller receiving a rotational force transmittedthereto, and a star wheel driven to rotate the driving roller rotating.

In this arrangement, the second transport means located downstream ofthe first transport means includes the plural roller pairs arranged inthe direction perpendicular to the transport direction, each of theplural roller pairs comprising the driving roller receiving a rotationalforce transmitted thereto, and the star wheel driven to rotate by thedriving roller rotating. Accordingly, the roller pairs forming thesecond transport means can be made different in nipping pressure fromeach other easily by adjusting the force of pressing the star wheelagainst the driving roller. Even when the roller pairs of the secondtransport means are made to have different nipping pressures within arange that is lower than the nipping pressure of the first transportmeans, such different nipping pressures will not influence over a largearea of the surface of the recording medium.

(8) A carriage unit having an ink head configured to jet ink against therecording medium is disposed between the first and second transportmeans arranged in the recording medium transport direction toreciprocate in the direction perpendicular to the recording mediumtransport direction.

In this arrangement, the first transport means and the second transportmeans are arranged across the position of the carriage unit fromupstream to downstream in the recording medium transport direction.Accordingly, the recording medium having been transported to theposition of the carriage unit as the printing position by the firsttransport means and then printed with an image during passage throughthe printing position can be transported smoothly with deformation atangular portions thereof rectified by the roller pairs disposed atopposite ends in the direction perpendicular to the transport directionduring its passage through the second transport means.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side elevational view showing a portion of concern of aconventional recording apparatus.

FIG. 2 is a side elevational view illustrating a state where a deformedrecording medium is transported in another conventional recordingapparatus.

FIGS. 3A and 3B are a plan view and a side elevational view,respectively, showing a portion of concern of an ink jet printer as oneexample of recording apparatus according to an embodiment of the presentinvention.

FIGS. 4A and 4B are a plan view and a side elevational view,respectively, showing a portion of concern of an ink jet printer as oneexample of recording apparatus according to another embodiment of thepresent invention.

FIGS. 5A and 5B are a plan view and a side elevational view,respectively, showing a portion of concern of an ink jet printer as oneexample of recording apparatus according to yet another embodiment ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 3A and 3B are a plan view and a side elevational view,respectively, showing a portion of concern of an ink jet printer as oneexample of recording apparatus according to an embodiment of the presentinvention. In ink jet printer 10 of this embodiment, first transportmeans 11 and second transport means 12 are arranged across the printingposition where a carriage unit 2 and a platen 9 are located in thisorder from upstream to downstream in a direction in which a recordingmedium 1 is to be transported, as in the arrangement shown in FIG. 1.

The carriage unit 2 is mounted on a cartridge having an ink head 7configured to jet ink. The carriage unit 2 is guided along anon-illustrated guide shaft to reciprocate in the primary scanningdirection perpendicular to the recording medium 1 transport direction bydriving force transmitted thereto via a non-illustrated timing belt.During reciprocation the ink head 7 is fed with driving signals based onvideo signals through a non-illustrated flat cable or the like. Thus,the carriage unit 2 jets ink from the ink head 7 against the surface ofrecording medium 1 supported on the platen 9 to print an image whilereciprocating in the primary scanning direction.

The first transport means 11 includes plural roller pairs arranged inthe direction perpendicular to the recording medium 1 transportdirection, the plural roller pairs each comprising a first drivingroller 3 to which rotation is transmitted from a non-illustrated driversuch as a motor, and a first driven roller 4 to be driven to rotate bythe first driving roller 3 rotating. The first transport means 11transports recording medium 1 to the printing position where the inkhead 7 of the carriage unit 2 faces the platen 9 while nipping therecording medium 1 between the first driving roller 3 and the firstdriven roller 4. The first driven roller 4 is pressed against the firstdriving roller 3 at a predetermined pressing force, whereby the firsttransport means 11 exerts on the recording medium 1 a predeterminednipping pressure sufficient to transport recording medium 1.

The second transport means 12 includes plural roller pairs arranged inthe direction perpendicular to the recording medium 1 transportdirection, the plural roller pairs each comprising a second drivingroller 5 to which rotation is transmitted from a non-illustrated driversuch as a motor, and star wheels 6 a to 6 e as a second driven roller 4to be driven to rotate by the second driving roller 5 rotating. Thesecond transport means 12 transports recording medium 1 having passedthrough the printing position to a delivery section fitted with anon-illustrated ejected sheet tray while nipping recording medium 1between the second driving roller 5 and the star wheels 6 a to 6 e. Thestar wheels 6 a to 6 e are pressed against the second driving roller 5at a predetermined pressing force, whereby the second transport means 12exerts on recording medium 1 a predetermined nipping pressure sufficientto transport recording medium 1.

The first driving roller 3, the first driven roller 4 and second drivingroller 5 are each supported by respective of non-illustrated bearings.Though one roller forming part of each roller pair of the secondtransport means 12 is not limited to the star wheels 6 a to 6 e, acontact area in which recording medium 1 is contacted by the secondtransport means 12 should be as small as possible in view of highlikelihood that an image printed on recording medium 1 having passedthrough the printing position is still in an undried state.

In the second transport means 12, the star wheels 6 a to 6 e arevertically movably supported by spring members 8 a and 8 b so as to comeinto contact with or separate from the second driving roller 5positioned therebelow while being biased toward the periphery of thesecond driving roller 5. Spring members 8 a biasing the outermost starwheels 6 a and 6 e of the star wheels 6 a to 6 e forming the secondtransport means 12 at opposite ends in the primary scanning directionare each made to have a higher elastic force than each of spring members8 b biasing the other star wheels 6 b to 6 d and, hence, the nippingpressure of each of the opposite end star wheels 6 a and 6 e is higherthan that of each of the other star wheel 6 b to 6 d. It should be notedthat the nipping pressure exerted on recording medium 1 by the secondtransport means 12 is set sufficiently lower than that exerted onrecording medium 1 by the first transport means 11.

The spring member 8 is supported on a frame via a non-illustratedsupport.

Recording medium 1 is transported in the direction indicated by arrowwhile being nipped between the first driving roller 3 and the firstdriven roller 4. Recording medium 1 is temporarily halted with aprinting area thereof positioned just below the ink head 7 of thecarriage unit 2. During the temporary halt of recording medium 1, thecarriage unit 2 jets ink against recording medium 1 from the ink head 7in accordance with image data to print an image while moving toward oneside in the primary scanning direction. Upon arrival of the carriageunit 2 at one end in the primary scanning direction, the first drivingroller 3 and the first driven roller 4 advance recording medium 1 untila succeeding printing area to be printed next comes into position andthen stop advancing it. In this state the carriage unit 2 jets inkagainst recording medium 1 from the ink head 7 in accordance with imagedata to print an image while moving toward the other side in the primaryscanning direction. This series of operations is repeated to print animage on the whole surface of recording medium 1.

If the leading edge of recording medium 1 is in a downwardly deformedstate when it reaches the second transport means 12, recording medium 1is first brought into contact with the second driving roller 5 at itsleading edge and then transported as kept deformed downwardly as thesecond driving roller 5 rotates, thereby acting to press the star wheels6 a to 6 e upwardly against the elastic force of the spring member 8.

However, such deformation frequently occurs at angular portions ofrecording medium 1. The star wheels 6 a and 6 e located at opposite endsfor nipping angular portions on the leading edge side of recordingmedium 1 are biased by the spring member 8 a toward the second drivingroller 5 side with a stronger elastic force than the other star wheels 6b to 6 d and, hence, will not easily be displaced upward by suchdeformed angular portions of recording medium 1. The elastic force ofthe spring member 8 a is established so that the nipping pressurebetween the star wheel 6 a, 6 e and the second driving roller 5 becomeshigh enough to rectify such deformation at angular portions of recordingmedium 1. Accordingly, recording medium 1 is nipped between the seconddriving roller 5 and the star wheels 6 a to 6 e with its deformedangular portions rectified. In this way recording medium 1 can betransported in an ideal condition.

The nipping pressure between each of the star wheels 6 a to 6 e and theassociated second driving roller 5, which determines the elastic forceof each of the spring members 8 a and 8 b, is influenced by variousfactors including the distance from an adjacent one of the star wheels 6a to 6 e, the nipping pressure of the adjacent one of the star wheels 6a to 6 e, the distance from the first transport means 11, the height atwhich each of the star wheels 6 a to 6 e and the associated seconddriving roller 5 contact each other, and the thickness and quality ofrecording medium 1 to be transported. Therefore, the elastic force ofeach of the spring members 8 a and 8 b is experimentally established inview of these factors.

The nipping pressure between each of the star wheels 6 a to 6 e and theassociated second driving roller 5 can be varied not only by varying theelastic force of the spring members 8 a and 8 b but also by changing themounting method for or the mounted form of spring members 8 of a singletype or the like. Thus, the operation of mounting the spring members 8can be facilitated. Alternatively, it is possible to vary the nippingpressure between each of the star wheels 6 a to 6 e and the seconddriving roller 5 by varying the weight of each of the star wheels 6 a to6 e.

FIGS. 4A and 4B are a plan view and a side elevational view,respectively, showing a portion of concern of an ink jet printer as oneexample of recording apparatus according to another embodiment of thepresent invention. In ink jet printer 10 of this embodiment, the secondtransport means 12 includes opposite end star wheels 6 a and 6 e,central star wheel 6 c and intermediate star wheels 6 b and 6 d, whichare arranged in this order from upstream to downstream in the recordingmedium 1 transport direction. Thus, the star wheels 6 a to 6 b arearranged at plural positions in the recording medium 1 transportdirection so that the nipping position of each of the opposite end starwheels 6 a and 6 e having a relatively high nipping pressure fails tocoincide with that of any one of the other star wheels 6 b to 6 d.

With this arrangement, the relatively high nipping pressure of theopposite end star wheels 6 a and 6 e is not exerted on the leading edgeportion of recording medium 1 at the same time with the nipping pressureof the other star wheels 6 b to 6 d. Thus, there is no possibility thatlarge load fluctuations occur during passage of recording medium 1through the second transport means 12. For this reason, this arrangementcan assuredly rectify deformation at the angular portions of therecording medium 1 without any impediment to smooth transport ofrecording medium 1.

Further, since the plural second driving rollers 5 of the secondtransport means 12 are secured to a single rotating shaft, the starwheels 6 a to 6 e are positioned along the circumference of the seconddriving roller 5 as shown in FIG. 4B by establishing the plural nippingpositions between the second driving rollers 5 and the star wheels 6 ato 6 e in the recording medium 1 transport direction. Thus, recordingmedium 1 can be transported in a more ideal condition.

In order to reduce load fluctuations at the leading edge portion ofrecording medium 1 being transported, the nipping position of thecentral star wheel 6 c made to exert a lower nipping pressure than theopposite end star wheels 6 a and 6 c may conceivably be located mostupstream in the recording medium transport direction. By so doing, theleading edge portion of recording medium 1 reaching the second transportmeans 12 is first applied with a relatively low nipping pressure at acentral portion thereof which is subject to large deformation. In thiscase, the central star wheel 6 c, intermediate star wheels 6 b and 6 d,and opposite end star wheels 6 a and 6 e are arranged in this order fromupstream to downstream in the recording medium transport direction.

In the case where the second transport means 12 has three or morenipping positions in the recording medium 1 transport direction, threeor more nipping pressures may be established, provided that the oppositeend star wheels 6 a and 6 e have the highest nipping pressure. Thisarrangement is capable of rectifying deformation at the leading edgeportion of recording medium 1 more finely. In this case, if the centralstar wheel 6C and the opposite end star wheels 6 a and 6 e are locatedmost upstream and most downstream, respectively, in the recording medium1 transport direction, the leading edge portion of recording medium 1being transported is applied with gradually increasing nipping pressurewith no possibility of abruptly receiving a high nipping pressure,whereby recording medium 1 can be transported more smoothly.

Further, if the recording medium 1 transport speed of the secondtransport means 12 is set higher than that of the first transport means11, there is no possibility that recording medium 1 becomes deflected atthe printing position between the first transport means 11 and thesecond transport means 12 and, hence, it is possible to keep recordingmedium 1 in a favorable flat condition on the platen 9 thereby to keepthe image printing condition satisfactory. Also, tension working in thetransport direction is exerted on recording medium 1 being transported,so that deformation of recording medium 1 can be rectified moreeffectively.

FIGS. 5A and 5B are a plan view and a side elevational view,respectively, showing a portion of concern of an ink jet printer as oneexample of recording apparatus according to yet another embodiment ofthe present invention. In ink jet printer 10 of this embodiment, aplurality of second transport means 12 a and 12 b are arranged in therecording medium 1 transport direction.

This arrangement is capable of nipping recording medium 1 at two pointsin the transport direction during a period after passage of the trailingedge of recording medium 1 through the first transport means 11 untilarrival of the trailing edge at the second transport means 12.Accordingly, even if deformation occurs at angular portions of recordingmedium 1 on the trailing edge side, this arrangement can reliablyrectify such deformation by means of the second driving rollers 5 andthe star wheels 6 a to 6 e disposed at opposite ends in the directionperpendicular to the transport direction while keeping the surface ofrecording medium 1 parallel with the transport direction. Thus, it ispossible to continue smooth transport until the trailing edge ofrecording medium 1 passes through the second transport medium 12.

It should be noted that the present invention is applicable not only toink jet printers of the type configured to realize printing by jettingink but also to various types of recording apparatus. Accordingly, ifthere is no need to take into consideration a dry degree of an image onrecording medium 1 having passed through the printing position, each ofthe roller pairs of the second transport means 12 does not necessarilyneed to comprise star wheel but may comprise a cylindrical rollerinstead.

Also, the plural roller pairs need not necessarily be disposedsymmetrically with respect to the center position in directionperpendicular to the recording medium transport direction.

As has been described above, the present invention makes it possible totransport a recording medium 1 ideally regardless of the shape ofleading edge of the recording medium 1 as well as to minimize damage tothe recording medium 1. Though other methods of ideally transporting therecording medium 1 regardless of the shape of leading edge of therecording medium 1 are conceivable, the arrangement of the presentinvention makes it possible to realize such ideal transport with a lowerparts count as well as to increase and decrease the pressure with thesame form of structure. Thus, the present invention is also advantageousin terms of cost and allows the design of apparatus to be simplified.

1. A recording apparatus wherein: a recording medium is transported byfirst and second transport means nipping the recording medium; and thesecond transport means comprises plural roller pairs arranged in adirection perpendicular to a recording medium transport direction and isdisposed downstream of the first transport means in the recording mediumtransport direction, characterized in that each of the roller pairs ofthe second transport means is set to have a lower nipping pressure thanthe first transport means, while an outermost one of the roller pairsset to have a higher nipping pressure than the rest of the roller pairs.2. The recording apparatus according to claim 1, wherein the pluralroller pairs of the second transport means are disposed to have pluralnipping positions in the recording medium transport direction such thatthe outermost one of the plural roller pairs is different in nippingposition from the rest of the plural roller pairs.
 3. The recordingapparatus according to claim 1, wherein the plural roller pairs of thesecond transport means are disposed to have plural nipping positions inthe recording medium transport direction such that a central one of theplural roller pairs has a nipping position located most upstream.
 4. Therecording apparatus according to claim 1, wherein the plural rollerpairs of the second transport means are disposed to have plural nippingpositions in the recording medium transport direction such that any oneof the roller which is located immediately downstream of an upstream oneof the roller pairs has a higher nipping pressure than the upstream one.5. The recording apparatus according to claim 1, wherein the secondtransport means is configured to transport the recording medium at ahigher speed than the first transport means.
 6. The recording apparatusaccording to claim 1, wherein a plurality of such second transport meansare arranged in the recording medium transport direction.
 7. Therecording apparatus according to claim 1, wherein each of the rollerpairs forming the second transport means comprises a driving rollerreceiving a rotational force transmitted thereto, and a star wheeldriven to rotate by the driving roller rotating.
 8. The recordingapparatus according to claim 1, wherein a carriage unit having an inkhead configured to jet ink against the recording medium is disposedbetween the first and second transport means arranged in the recordingmedium transport direction to reciprocate in the direction perpendicularto the recording medium transport direction.